A spring vice of this type has been known (U.S. Pat. No. 4,872,645), which has a guide tube in which a threaded spindle is rotatably mounted. To mount the threaded spindle in the area of one of its ends, a bearing bush is provided at the corresponding end of the guide tube. The bearing bush is screwed onto the end of the guide tube and is secured thereon against rotation by means of a grooved pin. This bearing bush has a recessed through hole with an inwardly directed bearing web, which acts as a bearing ring of a thrust bearing. A supporting cylinder, which forms the second bearing ring of the thrust bearing, is screwed onto the threaded spindle or to the end of the threaded spindle. The bearing bush screwed onto one end of the guide tube has on the outside a radially outwardly projecting bearing web, which is directed toward the guide tube and acts as a stop for a tensioning claw that can be mounted on the bearing bush in a firmly seated manner. To mount the tensioning claw on the bearing bush, the tensioning claw is provided with a mounting cylinder, with the mounting hole of which the tensioning claw can be pushed over the bearing bush until it comes into contact with the circular bearing web of the bearing bush. To fix the angular position of the tensioning claw in relation to the bearing bush and conseqently in relation to the guide tube, a fastening screw is provided, which passes radially through the mounting cylinder and is screwed into a threaded hole of the bearing bush. To absorb the strong axial forces occurring during the tensioning of a coil spring, the mounting cylinder is axially stationarily fixed on the bearing bush by means of a threaded ring. The bearing bush is provided for this purpose with a corresponding external thread at an axially spaced location from its bearing web, and the said external thread projects as part of the bearing bush in the axial direction over the mounting cylinder of the tensioning claw, which mounting cylinder is mounted on the bearing bush.
To tension a coil spring, a second tensioning claw is provided, which has a guide cylinder, with which this tensioning claw is mounted on the guide tube axially displaceably. The guide tube has a longitudinal slot, which is open on one side at the end of the guide tube located opposite the bearing bush and through which a radial finger projects radially from the inside and projects beyond the guide tube radially in the outwardly direction. The radial finger is part of a threaded bush, which engages the threaded spindle and is guided axially displaceably with a slight clearance inside the guide tube, The radial finger is in functional connection with the guide cylinder of the second tensioning claw, so that the radial finger is adjustable in the axial direction during the actuation of the threaded spindle via the threaded bush, and the guide cylinder is axially displaced on the guide tube during this adjustment process. The guide cylinder has a receiving groove, which extends axially in a wedge-shaped manner and into which the radial finger of the threaded bush fittingly penetrates in the mounted state of the guide cylinder on the guide tube and it engages the said guide tube in a nearly clearance-free manner. The guide cylinder is pushed over the guide tube during mounting from the side opposite the bearing bush and has a threaded section projecting over the receiving groove toward the first tensioning claw. To secure the guide cylinder axially at the radial finger, a second threaded ring is provided, which is screwed onto the threaded section of the guide cylinder and absorbs the axial forces applied by the radial finger during the tensioning of a compression coil spring between the two tensioning claws. To actuate the threaded spindle, the said threaded spindle has a drive hexagon at its end located opposite the bearing bush, and the said drive hexagon is attached to the end of the threaded spindle located opposite the bearing bush and is fixed on the threaded spindle by means of a locking pin. To mount the threaded spindle in the area of its drive hexagon, which is arranged on the threaded spindle axially outside the guide tube, a cover is provided, which is inserted centered into the guide tube with a guide section and is held in the guide tube by means of a locking pin.
Exchangeability of the tensioning claws for adaptation to compression coil springs of different sizes is guaranteed due to the manner of fastening of the two tensioning claws with their mounting cylinder and guide cylinder on the bearing bush and at the radial finger, respectively, by means of the threaded rings. However, the replacement of the tensioning claws is relatively complicated. Furthermore, only relatively weak axial forces can be applied for tensioning compression coil springs due to the threaded rings provided for fastening the tensioning claws at the guide tube and at the radial finger, because the thread of the threaded rings breaks out under higher loads, especially in the case of axial forces exceeding 5,000 N. Moreover, replacement is rather complicated, because the screw connections must be loosened for replacing the tensioning claws. Since contamination is always present during use in workshops, there always is a risk of damage to the threaded connections between the mounting cylinder or the guide cylinder and the threaded rings, so that this also weakens the threaded connection. This weakening of the threaded connection facilitates the breaking out of the threaded connection, so that the maximum possible tensioning forces for tensioning a coil compression spring are reduced. In addition, the manufacturing costs are very high because of the complicated design of the prior-art spring vice.